Que. 1. What do you mean by term environment?

Ans. 1. It includes all external factors (living or non-living, material or non-material) which surround men.

Que. 2. Enumerate few adverse environmental factors affecting people’s health.

Ans. 2. The environmental factors which affect health of people are as follows –

• Air Pollution
• Water Pollution
• Soil Pollution
• Poor housing conditions
• Presence of animal reservoirs
• Presence of Insect vectors of disease
• Unhygienic disposal of human excreta & refuse

Que. 3. What do you mean by term environmental sanitation?

Ans. 3. The control of all those factors in man’s physical environment which exercise or may exercise a deleterious effect on his physical development, health & survival (WHO).

Que. 4. Define safe and wholesome water.

Ans. 4. Safe & wholesome water has been defined as water that is –

• Free from pathogenic organisms or agents
• Free from harmful chemical substances
• Pleasant to the taste
• Free from color & Odour
• Usable for domestic purposes

Water is said to be polluted water if it does not follow above criteria.

Que. 5. In urban areas, how much water supply is considered adequate to meet the domestic needs, per capita per day?

Ans. 5. 150-200 liters per capita per day.

Que. 6. What was the target of water supply per capita in India for rural areas?

Ans. 6. 40 liters of water supply per capita per day.

Que. 7. What do you mean by safe yield of the water source?

Ans. 7. The safe yield of the water source must be sufficient to serve the population, expected at the design period which may be 10-40 years in future. It is generally defined as the yield of water that is adequate for 95% of the year.

Que. 8. Which are the criteria that water source must conform?

Ans. 8. Those criteria are as follows –

• The quantity must be sufficient to meet the present and future requirements.
• The quality of water must be acceptable.

Que. 9. Give examples of surface water.

Ans. 9. Rivers, tanks, lakes, wadis, man-made reservoirs & sea water.

Que. 10. What do you mean by impounding reservoirs?

Ans. 10. These are artificial lakes constructed by earthwork or masonry in which large quantities of surface water is stored.

Que. 11. Name three cities deriving water supply from impounding reservoirs.

Ans. 11. Mumbai, Chennai & Nagpur.

Que. 12. Which is the most cheap & most practical means of providing water to small communities?

Ans. 12. Ground water.

Que. 13. What are the advantages of ground water?

Ans. 13. The advantages of ground water are as follows –

• Likely to be free from pathogenic agents.
• Usually requires no treatment.
• Supply is likely to be certain even during dry season.
• Less subject to contamination than surface water.

Que. 14. Which are the disadvantages of ground water?

Ans. 14. The disadvantages of ground water are as follows –

• High in mineral content.
• It requires pumping or some mechanism to uplift the water.

Que. 15. What do you mean by shallow wells?

Ans. 15. Shallow well derives subsoil water i.e. the water from above the first impervious layer in the ground. They yield limited quantities of water and water is liable for marked contamination.

Que. 16. What do you mean by deep wells?

Ans. 16. A deep well derives its water from the water bearing stratum below the first impervious layer in the ground. Deep wells are dug by machine and may be several hundred meters deep. Deep well provides safest water and are often the most satisfactory source of water supply.

Que. 17. What do you mean by artesian wells?

Ans. 17. Not common in India, are a kind of deep wells in which water rises above the level of ground water, because it is held under pressure between two impervious strata.

Que. 18. What do you mean by a sanitary well?

Ans. 18. A sanitary well is one which is properly situated, well-constructed and protected against contamination, with a view to yield a supply of safe water.

Que. 19. Which are the indicators of water pollution?

Ans. 19. The indicators of water pollution are as follows –

• Amount of total suspended solids
• Biochemical oxygen demand (BOD) at 20-degree C
• Concentration of chlorides, nitrogen & phosphorus
• Absence of dissolved oxygen

Que. 20. Name water borne viral diseases.

Ans. 20. Viral Hepatitis A & E, poliomyelitis (Eradicated from India) & rotavirus diarrhea in young children.

Que. 21. Name water borne bacterial diseases.

Ans. 21. Typhoid & paratyphoid fever, bacillary dysentery, cholera & E. coli diarrhea.

Que. 22. Name water borne protozoal diseases.

Ans. 22. Amoebiasis & giardiasis.

Que. 23. Name water borne diseases caused by the presence of an aquatic host cyclops.

Ans. 23. Guinea worm & fish tapeworm diseases.

Que. 24. Name water borne disease caused by the presence of an aquatic host snail.

Ans. 24. Schistosomiasis.

Que. 25. Why fluoride is considered as a double edged sword?

Ans. 25. Excess of fluoride in water may cause dental & skeletal fluorosis while lack of fluoride in water may cause dental caries, thus acting as a double edged sword.

Que. 26. Name the diseases transmitted because of inadequate use of water.

Ans. 26. Shigellosis, trachoma, conjunctivitis, ascariasis & scabies.

Que. 27. In which year was the water (prevention & control of pollution) act passed by Indian parliament?

Ans. 27. 1974.

Que. 28. What are the components of typical water purification system?

Ans. 28.  The components include one or more of the following measures –

• Storage
• Filtration
• Disinfection

Que. 29. What is the optimum period of storage of river water?

Ans. 29. About 10-14 days.

Que. 30. Which are the types of filters used for large scale water purification?

Ans. 30. Two types of filters are used –

• Slow sand or biological filter
• Rapid sand or mechanical filter

Que. 31. Which are the various elements of a slow sand filter?

Ans. 31. The various elements are –

• Supernatant or raw water
• A bed of graded sand particles
• An underdrainage system
• A system of filter control valves

Que. 32. What is the thickness of sand bed in slow sand filter?

Ans. 32. About one meter.

Que. 33. What is the effective diameter of sand particles in sand bed of biological filter?

Ans. 33. 0.2-0.3 mm.

Que. 34. What is the designated rate of filtration of water in slow sand filter?

Ans. 34. 0.1-0.4 meter cube/hour/square meter of sand bed surface.

Que. 35. What do you mean by ripening of the filter?

Ans. 35. The formation of vital layer over the surface of the sand bed is known as ripening of filter.

Que. 36. What do you mean by vital layer?

Ans. 36. Vital layer is slimy & gelatinous and consists of thread like algae and numerous forms of life like plankton, diatoms and bacteria. Formation of vital layer over the surface of sand bed turns a newly laid slow sand filter to a biological filter in true sense.

Que. 37. What is the role of Venturi meter in filter control?

Ans. 37. It measures the sand bed resistance or loss of head.

Que. 38. What are the advantages of slow sand filter?

Ans. 38. The advantages of slow sand filters are –

• Simple to construct & operate
• Cheaper
• High quality water

Que. 39. Which are the types of rapid sand filters used in water purification?

Ans. 39. Two types –

• Gravity type (Paterson’s filter)
• Pressure type (Candy’ filter)

Que. 40. Which are the steps involved in the purification of water by rapid sand filters?

Ans. 40. The steps involved are –

• Coagulation
• Rapid Mixing
• Flocculation
• Sedimentation
• Filtration

Que. 41. What is the effective size of sand particles in rapid sand filter?

Ans. 41. 0.4-0.7 mm.

Que. 42. What is the rate of filtration of rapid sand filters?

Ans. 42. 5-15-meter cube/ meter square/hour.

Que. 43. What do you mean by back washing?

Ans. 43. A method of washing rapid sand filters which is done by reversing the flow of water through the sand bed.

Que. 44. What are the advantages of rapid sand filter?

Ans. 44. The advantages of rapid sand filters are as follows –

• Preliminary storage is not required.
• Can deal with raw water directly
• Occupies less space
• More flexibility in operations
• Filtration is rapid
• Washing of filter is easy

Que. 45. What is the chlorine demand of the water?

Ans. 45. The chlorine demand of water is the difference between the amount of chlorine added to the water, and the amount of residual chlorine remaining at the end of a specific period of contact (usually 60 minutes), at a given temperature and pH of water.

Que. 46. What is the minimum recommended free chlorine for one hour?

Ans. 46. 0.5 mg/L

Que. 47. Which are the forms of chlorine to be applied for disinfecting large bodies of water?

Ans. 47. The forms of chlorine are –

• Chlorine gas
• Chloramine
• Perchloron

Que. 48. What is the use of orthotolidine (OT) test?

Ans. 48. Measures both free & combined chlorine with speed & accuracy.

Que. 49. What is the use of Orthotolidine-Arsenite (OTA) test?

Ans. 49. Measures the free and combined chlorine residuals separately.

Que. 50. Which are the methods used for household purification of water?

Ans. 50. The methods are as follows –

• Boiling
• Chemical disinfection
• Filtration
• U-V radiation
• Multi stage reverse osmosis purification of water.

Que. 51. Which are the chemicals used for household purification of water?

Ans. 51. The chemicals used are as follows –

• Bleaching powder
• Chlorine solution
• High test hypochlorite
• Chlorine tablets
• Iodine &
• Potassium permanganate

Que. 52. Which are the filters used for water purification on a small scale?

Ans. 52. The filters used are as follows –

• Pasteur Chamber land filter
• Berkefeld filter and
• Katadyn filter

Que. 53. What is the role of multi stage reverse osmosis purification of water?

Ans. 53. Multistage reverse osmosis purification of water is used to make water both chemically and microbiologically safe by reducing the total dissolved solids, hardness, heavy metals and disease causing bacteria, virus, protozoa and cysts.

Que. 54. Which is the most effective & cheapest method of disinfecting well?

Ans. 54. Bleaching powder.

Que. 55. Which instrument is used to estimate chlorine demand of well water?

Ans. 55. Horrock’s Apparatus.

Que. 56. Which is the method used for disinfecting well water during an emergency?

Ans. 56. Double pot method.

Que. 57. Which are the physical parameters of quality drinking water?

Ans. 57. Physical parameters of drinking water are –

• Turbidity
• Taste & odor
• Temperature
• Color

Que. 58. What is the level of ammonia in ground & surface water?

Ans. 58. Usually below 0.2 mg/L.

Que. 59. What is the range of pH acceptable for drinking water?

Ans. 59. Between 6.5 -8.5.

Que. 60. Which people are at greatest risk of water borne diseases?

Ans. 60. Infants and young children, people who are living under insanitary conditions, the sick & the elderly.

Que. 61. Which are the bacteriological indicators suggestive of faecal pollution of water?

Ans. 61. Bacteriological indicators suggestive of faecal pollution of water are –

• Coliform organisms
• Faecal streptococci
• Perfringens

Que. 62. What does presence of faecal streptococci in water suggest?

Ans. 62. Confirmation of recent faecal pollution of water.

Que. 63. What does presence of spores of Cl. Perfringens in water suggest?

Ans. 63. Faecal contamination of water. The presence of spores of Cl. Perfringens, in the absence of the coliform group, suggests that faecal contamination occurred at some remote time.

It’s presence in filtered supplies may indicate deficiency in filtration practice.

Que. 64. Which are the tests included in complete bacteriological examination of drinking water?

Ans. 64. The tests included are –

• Presumptive coliform test
• Test for detection of faecal streptococci
• Test for detection of Cl. Perfringens
• Colony count

Que. 65. What are the types of presumptive coliform test?

Ans. 65. The types of presumptive coliform test are as follows –

• Multiple tube method
• Membrane filtration technique

Que. 66. What does constitute the hardness of water?

Ans. 66. The hardness in water is caused mainly by four dissolved compounds. These are –

• Calcium bicarbonate
• Magnesium bicarbonate
• Calcium sulphate
• Magnesium sulphate

Presence of any of these compounds causes hardness of water.

Que.  67. What does cause carbonate or temporary hardness of water?

Ans. 67. Presence of Calcium & Magnesium bicarbonates.

Que. 68. What does cause non-carbonate or permanent hardness of water?

Ans. 68. Sulphates, chlorides and nitrates of Calcium & Magnesium.

Que. 69. How will you classify hardness in water?

Ans. 69.

Que. 70. What should be the hardness of drinking water?

Ans. 70. Drinking water should be moderately hard.

Que. 71. At what level of hardness, will you recommend softening of water?

Ans. 71. When the hardness exceeds 3 m eq/L (150 mg/L).

Que. 72. What are the disadvantages of hardness of water?

Ans. 72. The disadvantages of hardness of water are as follows –

• Consumes more soap and detergent
• On heating causes scaling of boilers
• Adversely affect cooking, natural color and appearance is lost.
• Fabrics have shorter life
• Shortens the life of pipes and fixtures

Que. 73. Which are the methods used for removal of temporary hardness of water?

Ans. 73. The methods are as follows –

• Boiling
• Addition of lime
• Addition of sodium carbonate
• Permutit process

Que. 74. Which are the methods used for removal of permanent hardness of water?

Ans. 74. The methods are as follows –

• Addition of Sodium carbonate
• Base Exchange process

Que. 75. What should be the optimum concentration of fluorine in drinking water?

Ans. 75. 0.5-0.8 ppm.

Que. 76. What do you mean by term fluoridation of water?

Ans. 76. It is the process of supplementing the natural fluoride content of potable waters to the point of optimum concentration for protection against dental caries.

Que. 77. What do you mean by term defluoridation of water?

Ans. 77. Water with high fluoride levels is defluoridated by phosphates to reduce fluorides to optimum level of protection against dental and skeletal fluorosis.

Que. 78. What are health hazards associated with swimming pools?

Ans. 78. The health hazards associated with swimming pools are as follows –

• Fungal & viral infection of the skin
• Infections of eye, ear, nose & throat
• Upper respiratory tract infections
• Intestinal infections
• Accidents

Que. 79. What does conservation of water resources require?

Ans. 79. These require –

• Prevention of wastage
• Water harvesting

Que. 80. How is air rendered impure?

Ans. 80. Air is rendered impure by –

• Respiration of men and animals
• Combustion of coal, gas, oil etc.
• Decomposition of organic matters
• Trade, traffic & industries

Que. 81. Which are the indices of thermal comfort?

Ans. 81. The indices of thermal comfort are –

• Air temperature
• Air temperature & humidity
• Cooling power of air
• Effective temperature
• Corrected Effective temperature

Que. 82. What do you mean by cooling power of the air?

Ans. 82. Air temperature, humidity and air movement were expressed together as cooling power of the air.

Que. 83. Which was the instrument used to measure cooling power of the air?

Ans. 83. Kata thermometer (designed by Hill).

Que. 84. What do you mean by effective temperature?

Ans. 84. It is an arbitrary index which combines into a single value the effect of temperature, humidity & movement of the internal air on the sensation of warmth or cold felt by the human body.

Que. 85. What do you mean by corrected effective temperature?

Ans. 85. It deals with all the 4 factors namely air temperature, velocity, humidity & mean radiant heat on a scale.

Que. 86. How will you evaluate comfort zones in India?

Ans. 86.

Que. 87. What are the sources of air pollution?

Ans. 87. The important sources of air pollution are as follows –

• Automobiles
• Industries
• Domestic sources
• Smoking
• Burning refuse/Incineration
• Pesticide sprays
• Nuclear energy programs

Que. 88. How is air pollutant carbon monoxide produced?

Ans. 88. Produced by incomplete combustion of carbon containing materials, such as in automobiles, industrial process, heating facilities & Incineration.

Que. 89. How is air pollutant SO2 produced?

Ans. 89. Produced by the combustion of Sulphur containing fossil fuel, the smelting of Sulphur containing ores & other industrial processes. Domestic fires, power generation & motor vehicles are other important sources of SO2.

Que. 90. Which are the health hazards of air pollutant SO2 excess in air?

Ans. 90. The health hazards are as follows –

• Inflammation of respiratory tract
• Aggravation of asthma & chronic bronchitis
• Makes prone for respiratory infections
• Irritation of eyes
• Hospital admission for cardiac disease

Que. 91. How is air pollutant lead produced?

Ans. 91. Mainly by combustion of alkyl lead additives in major fuels accounts for the major part of all lead emissions in to the atmosphere. The mining & smeltering of lead is also major cause in some areas.

Que. 92. Which are the sources of hydrocarbons as air pollutant?

Ans. 92. Incineration, combustion of coal, wood & processing & use of petroleum.

Que. 93. What is the recommended limit of ozone in air?

Ans. 93. 100 micrograms/cubic meter of 8-hours mean.

Que. 94. Name the most potent carcinogens among the known PAHs.

Ans. 94. BaP (Benzo a pyrene).

Que. 95. Which are the people on highest exposure to PAHs?

Ans. 95. Smokers, people who live with or work with smokers, roofers, road builders and people who live near major highways or industrial sources.

Que. 96. Which are the major sources of indoor air pollution?

Ans. 96. Combustion of solid fuels indoors, tobacco smoking, outdoor air pollutants, emissions from construction and furnishings and improper maintenance of ventilation & air conditioning.

Que. 97. What are the health hazards of indoor air pollution?

Ans. 97. ARI in young children, pneumonia, chronic lung diseases, cancer, adverse pregnancy outcomes (still birth).

Que. 98. Which are the best indicators of air pollution?

Ans. 98. SO2, smoke & suspended particles.

Que. 99. Which are the health hazards of air pollution?

Ans. 99. The health hazards of air pollution are as follows –

• Acute bronchitis
• Suffocation
• Chronic bronchitis
• Lung cancer
• Bronchial asthma
• Emphysema
• Respiratory allergies
• Impaired neuropsychological development in children (due to lead).

Que. 100. How will you prevent & control air pollution?

Ans. 100. Following measures are recommended –

• Containment – e.g. arrestors for removal of contaminants
• Replacement with new technology
• Dilution – e.g. green belts between industrial and residential areas
• Legislation e.g. The AIR (prevention and control of pollution) Act in 1981.
• International action – e.g. international network of labs for monitoring & study of air pollution.

Que. 101. Which are the methods employed for disinfection of air in OT & infectious disease wards?

Ans. 101. U-V radiation.

Que. 102. What are the standards of ventilation?

Ans. 102. The standards of ventilation are as follows –

• Cubic Space – Recommended is 300-3000 cubic feet per person per hour. This standard is no longer followed.
• Air Change – Recommended that in the living rooms, there should be 2-3 air change in one hour & in work room & assemblies 4-6 air change per hour.
• Floor space – Recommended 50-100 square feet per person.

Que. 103. What are the types of artificial/mechanical ventilation?

Ans. 103. The types of artificial or mechanical ventilation are –

• Exhaust Ventilation
• Plenum Ventilation
• Balanced Ventilation
• Air-conditioning

Que. 103. When will you consider light to be sufficient?

Ans. 103. An illumination of 15-20 foot candles is accepted as a basic minimum for satisfactory vision.

Que. 104. What are the requirements of good lighting?

Ans. 104. Good lighting should have following characteristics –

• Sufficiency
• Uniform distribution
• Absence of glare
• Absence of sharp shadows
• Steadiness
• Color of light
• Contrasting surroundings

Que. 105. What does luminous intensity measure and in what standard units?

Ans. 105. Brightness of point source. Standard unit is candela.

Que. 106. What does luminous flux measure and in what units?

Ans. 106. Flow of light. Standard unit is Lumen.

Que. 107. What does illumination illuminance measure and in what units?

Ans. 107. Amount of light reaching surface. Standard unit is lux.

Que. 108. What does brightness luminance measure and in what units?

Ans. 108. Amount of light re-emitted by surface. Standard unit is Lambert.

Que. 109. Which factor is used for measurement of daylight?

Ans. 109. Daylight factor. Measured by daylight factor meter.

Que. 110. Which are the methods of artificial illumination?

Ans. 110. The methods of artificial illumination are –

• Filament lamps
• Fluorescent Lamps.

Que. 111. What is the recommended illumination for casual reading?

Ans. 111. 100 Lux.

Que. 112. What is the recommended illumination for general office work?

Ans. 112. 400 Lux.

Que. 113. What is the recommended illumination for watch making?

Ans. 113. 2000-3000 Lux.

Que. 114. What are the health benefits of lighting?

Ans. 114.  The health benefits of lighting are as follows –

• Positive effect on biological rhythm of body temperature
• Physical activity improved
• Stimulation of melanin synthesis
• Activation of precursors of vitamin D, adrenocortical secretion
• Improved food consumption
• In vitro degradation of bilirubin (natural day light).

Que. 115. What do you mean by noise pollution?

Ans. 115. To signify the vast cacophony of sounds that are being produced in the modern life, leading to health hazards.

Que. 116. What are the important properties of noise?

Ans. 116. The important properties of noise are –

• Loudness or intensity
• Frequency

Que. 117. What limit of daily exposure to noise people can tolerate without substantial damage to their hearing?

Ans. 117. 85 dB

Que. 118. Which instrument does measure the intensity of sound in dB or dB (A)?

Ans. 118. Sound level meter.

Que. 119. Which instrument does measure hearing ability?

Ans. 119. Audiometer.

Que. 120. What do you mean by Phon?

Ans. 120. The phon is a psycho-acoustic index of loudness. It takes into consideration both intensity & frequency.

Que. 121. What are the health hazards of radiation?

Ans. 121. The health hazards of radiation are as follows –

• Chromosomal & point mutations
• Radiation sickness
• Acute radiation syndrome
• Carcinogenesis
• Leukemia
• Foetal development anomalies
• Shortening of life

Que. 122. What is the permissible dose of radiation from man-made sources?

Ans. 122. Should not exceed 5 rad a year.

Que. 123. What do you mean by rad?

Ans. 123. Rad is the unit of adsorbed dose of radiation. It is the amount of radioactive energy absorbed per gram of tissues or any material. Newer SI unit Gray is replacing the rad.

Que. 124. What do you mean by Rem?

Ans. 124. Rem is the product of absorbed dose of radiation & the modifying factors. The Rem indicates degree of potential danger to health. Newer SI unit Sievert is replacing the rem.

Que. 125. What do you mean by Roentgen?

Ans. 125. Roentgen is the unit of exposure to radiation. Newer SI unit Coulomb per kilogram is replacing the Roentgen.

Que. 126. What do you mean by Barograph?

Ans. 126. Barograph is an instrument for obtaining a continuous record of atmospheric pressure.

Que. 127. Which are the health conditions resulting from sudden exposure to high altitude?

Ans. 127. Resulting health conditions are –

• Acute mountain sickness
• Pulmonary oedema

Que. 128. Which are the physiological effects of exposure to low pressure?

Ans. 128. The physiological effects are –

• Increase in respiration
• Increase in concentration of Hemoglobin
• Increase in Cardiac output

Que. 129. What are the methods of measuring air temperature?

Ans. 129.  The methods of measuring air temperature are as follows –

• Dry bulb thermometer
• Wet bulb thermometer
• Maximum & Minimum thermometer
• Six’s maximum & minimum thermometer
• Globe thermometer
• Wet globe thermometer
• Silvered thermometer
• Kata thermometer

Que. 130. What is the use of globe thermometer?

Ans. 130. Used for direct measurement of the mean radiant temperature of the surroundings.

Que. 131. What are the effects of heat stress?

Ans. 131. The effects of heat stress are as follows –

• Heat Stroke
• Heat Hyperpyrexia
• Heat Exhaustion
• Heat Cramps
• Heat Syncope

Que. 132. What are the effects of cold stress?

Ans. 132. The effects of cold stress are as follows –

• Immersion or trench foot
• Frostbite
• Hypothermia

Que. 133. Which are the characteristic features of hypothermia?

Ans. 133. The characteristic features of hypothermia are as follows –

• Numbness & loss of sensation
• Muscular weakness
• Desire for sleep
• Coma & death

Que. 134. What is the use of anemometer?

Ans. 134. It is used to measure air velocity.

Que. 135. What is the use of wind vane?

Ans. 135. It is used as an instrument to observe wind direction.

Que. 136. Which are the social goals of housing?

Ans. 136. The social goals of housing are as follows –

• Shelter
• Family life
• Access to community facilities
• Family participation in community life
• Economic stability

Que. 137. What are the housing standards regarding setback?

Ans. 137. In rural areas, the buildup area should not exceed 1/3^rd of the total area while in urban areas, the buildup area may be up to 2/3^rd of the total area.

Que. 138. What are the housing standards regarding roof?

Ans. 138. The height of the roof should not be less than 10 feet (3 Meters) in the absence of air-conditioning for comfort. The roof should have a low heat transmittance coefficient.

Que. 139. What are the housing standards regarding floor area?

Ans. 139. Floor area of a living room should be at least 120 square feet (12 Sq. m.) for occupancy by more than one person or at least 100 sq. feet (10 sq. m.), for occupancy by a single person.

Que. 140. What are the housing standards regarding cubic space?

Ans. 140. An air space of at least 500 cubic feet per capita, preferably 1000 cubic feet.

Que. 141. What is the housing standards regarding lighting?

Ans. 141. The day light factor should exceed 1% over half of the floor area.

Que. 142. Enumerate health hazards of housing.

Ans. 142. The health hazards of housing are –

• Respiratory infections
• Skin infections
• Plague
• Arthropod borne diseases
• Accidents
• Psychosocial effects

Que. 143. What is the rubbish?

Ans. 143. It consists of paper, clothing, bits of wood, metal, glass, dust & dirt. It is a type of domestic refuse.

Que. 144. What do you mean by Garbage?

Ans. 144. Garbage is a type of domestic refuse, arising from the preparation, cooking and consumption of foods.

Que. 145. What do you mean by Litter?

Ans. 145. It is a type of stable refuse and contains mainly animal droppings & left over animal feeds.

Que. 146. What are the reasons of considering solid waste as a health hazard?

Ans. 146. The reasons are –

• It decomposes and favors fly breeding
• It attracts rodents and vermin
• Pathogen present in waste may be transmitted back to humans through flies and dust
• Possibility of water and soil pollution
• Creates unsightly appearance and nuisance from bad odors
• Increased incidence of vector borne diseases

Que. 147. Which are the important methods of refuse disposal?

Ans. 147. The important methods of refuse disposal are as follows –

• Dumping
• Controlled tipping or sanitary landfill
• Incineration
• Composting
• Manure pits
• Burial

Que. 148. Which are the methods used for sanitary landfill or controlled tipping?

Ans. 148. The methods used are –

• The trench method
• The ramp method
• The area method

Que. 149. Which is the best method of hospital waste disposal?

Ans. 149. Incineration.

Que. 150. Which are the commonly used methods of composting?

Ans. 150. The commonly used methods of composting are –

• Bangalore Method (Hot fermentation Process) – Anaerobic method
• Mechanical Method – Aerobic method

Que. 151. Which is the method of choice of refuse disposal for small camps?

Ans. 151. Burial.

Que. 152. Which are the health hazards of improper excreta disposal?

Ans. 152. The health hazards are as follows –

• Soil pollution
• Water pollution
• Contamination of foods
• Propagation of flies

Que. 153. Which are the diseases resulting from improper excreta disposal?

Ans. 153. The resulting diseases are –

• Typhoid & paratyphoid fevers
• Dysenteries
• Diarrhoea
• Cholera
• Hookworm disease
• Ascariasis
• Viral Hepatitis

Que. 154. How disease is carried from excreta to a new host?

Ans. 154. The disease agent is carried from excreta to a new host through –

• Water
• Fingers
• Flies
• Soil
• Food

Que. 155. Which are the methods of excreta disposal suitable for camps & temporary use?

Ans. 155. Suitable methods are as follows –

• Shallow trench latrine
• Deep trench latrine
• Pit latrine
• Bore hole latrine

Que. 156. Which are the types of sanitary latrine?

Ans. 156. Types of sanitary latrines are –

• Bore hole latrine
• Dug well or pit latrine
• Water seal type of latrine
• Septic tank
• Aqua privy

Que. 157. Which are the criteria to fulfil by a sanitary latrine?

Ans. 157. The criteria are as follows –

• Excreta does not pollute soil
• Excreta does not contaminate the ground or surface water
• Excreta is not accessible to flies, rodents, animals & other vehicles of transmission
• Excreta does not produce odour or unsightly appearance

Que. 158. What are the functions of a water seal in water seal latrine?

Ans. 158. The functions of water seal latrine are –

• Prevent access to flies
• Prevent bad odour and smell
• Once the latrine is flushed, night soil is no longer visible.

Que. 159. What are the stages of purification of sewage in a septic tank?

Ans. 159. Anaerobic digestion —- in septic tank proper

Aerobic oxidation ——– outside the septic tank, in the sub-soil.

Que. 160. What is sewage?

Ans. 160. Sewage is waste water from a community containing solid & liquid excreta derived from households and other sources.

Que. 161. What are the health hazards of improper sewage disposal?

Ans. 161. The health hazards are given below –

• Creation of nuisance, unsightliness & unpleasant odours
• Breeding of flies & mosquitoes
• Pollution of soil & water supplies
• Contamination of food
• Increased incidence of enteric & helminthic disease

Que. 162. How is strength of sewage expressed?

Ans. 162. Strength of sewage may be expressed in following ways –

• Biochemical Oxygen Demand (BOD)
• Chemical Oxygen Demand (COD)
• Suspended solids

Que. 163. When will you say sewage to be strong one?

Ans. 163. When –

• BOD is equal to or more than 300 mg/L
• Amount of suspended solids is 500 mg/L

Que. 164. In sewerage system, which are the options of disposal of effluents?

Ans. 164. The options of disposal of effluents are –

• Sea outfall
• River outfall
• Sewage farming
• Oxidation ponds
• Oxidation ditches

Que. 165. Give examples of arthropod borne diseases transmitted by direct contact.

Ans. 165. Scabies & pediculosis.

Que. 166. Give examples of arthropod borne diseases spread by mechanical transmission.

Ans. 166. Typhoid, paratyphoid, diarrhoea, dysentery, food poisoning & Trachoma.

Que. 167. What are the types of biological transmission?

Ans. 167. The types of biological transmission are –

• Propagative
• Cyclo-propagative
• Cyclo-developmental

Que. 168. What do you mean by propagative biological transmission?

Ans. 168. When the disease agent undergoes no cyclical change, but multiplies in the body of the vector, transmission is said to be propagative e.g. plague bacilli in rat flea.

Que. 169. What do you mean by Cyclo-propagative biological transmission?

Ans. 169. The disease agent undergoes cyclical change, and multiplies in the body of arthropod e.g. malarial parasite in mosquitoes.

Que. 170. What do you mean by Cyclo-developmental biological transmission?

Ans. 170. When disease agent undergoes cyclical change but does not multiply in the body of arthropod e.g. filarial parasite in Culex mosquitoes.

Que. 171. What do you mean by term definitive host?

Ans. 171. The host in which the sexual cycle of the agent occurs e.g. mosquito in malaria.

Que. 172. What do you mean by term intermediate host?

Ans. 172. The host in which the asexual cycle of the disease agent occurs e.g. Mosquito in filaria.

Que. 173. What are the general principles of arthropod control?

Ans. 173. The general principles of arthropod control are as follows –

• Environmental Control
• Chemical Control
• Biological Control
• Genetic Control
• Integrated approach of control

Que. 174. Give one example of biological control.

Ans. 174. Use of larvivorous fish especially Gambusia for mosquito control.

Que. 175. Give examples of environmental control.

Ans. 175. Examples of environmental control are as follows –

• Elimination of breeding places of arthropods
• Filling & drainage operations
• Planned water management
• Provision of piped water supply etc.

Que. 176. Which mosquito is also known as Nuisance mosquitoes?

Ans. 176. Culex mosquitoes.

Que. 177. What is the peak biting time of Culex mosquitoes?

Ans. 177. Midnight. Legs below knee are preferred site of biting.

Que. 178. What are the breeding sites of Culex mosquitoes?

Ans. 178. Breeds in dirty water collections & in fact all types of water collections.

Que. 179. Which mosquito is also known as Tiger mosquito?

Ans. 179. Aedes mosquitoes.

Que. 180. What are the breeding sites of Aedes mosquitoes?

Ans. 180. Breeds in artificial accumulation of water in and around human dwellings.

Que. 181. What is the peak biting time of Aedes mosquitoes?

Ans. 181. Day time.

Que. 182. What are the breeding sites of Mansonia mosquitoes?

Ans. 182. Breed in ponds & lakes containing aquatic plants like Pistia stratiotes & water hyacinth.

Que. 183. What are the preferred breeding sites of Anopheles mosquitoes?

Ans. 183. Clean water.

Que. 184. Which are the diseases transmitted by Anopheles mosquitoes?

Ans. 184. Malaria & Filaria (Not in India).

Que. 185. Which are the diseases transmitted by Culex mosquitoes?

Ans. 185. Bancroftian filariasis, Japanese Encephalitis, West Nile fever & Viral arthritis.

Que. 186. Which are the diseases transmitted by Aedes mosquitoes?

Ans. 186. Yellow fever (not in India), Dengue, dengue haemorrhagic fever, Chikungunya fever, Rift valley fever & Filaria (not in India).

Que. 187. Which are the diseases transmitted by Mansonoides mosquitoes?

Ans. 187. Brugian filariasis & Chikungunya fever.

Que. 188. Which are the fishes used for biological control of mosquito larvae?

Ans. 188. Gambusia affinis & Lebister reticulatus.

Que. 189. Under chemical control, which are the commonly used mosquito larvicides?

Ans. 189. Mineral oils, Paris green & Synthetic insecticides.

Que. 190. Which are the insecticides used in residual sprays for mosquito control?

Ans. 190. DDT, Lindane, Malathion & OMS-33.

Que. 191. Which are the insecticides used in space sprays for mosquito control?

Ans. 191. Pyrethrum extract & Malathion & fenitrothion (ULV fogging).

Que. 192. Name the commonly used mosquito repellents.

Ans. 192. Commonly used mosquito repellents are –

• Diethyltoluamide/DEET – Most effective
• Indalone
• Dimethyl phthalate
• Dimethyl carbate
• Ethyl hexanediol

Que. 193. What is the dose and average duration of effectiveness for malathion in residual sprays?

Ans. 193. 2 gm/meter square; 3 months.

Que. 194. What is the dose and average duration of effectiveness for DDT in residual sprays?

Ans. 194. 1-2 gm/meter square; 6-12 months.

Que. 195. Which are the important breeding places of houseflies?

Ans. 195. Important breeding places of houseflies are –

• Fresh horse manure
• Human excreta
• Manure of other animals
• Garbage
• Decaying fruits & vegetables
• Rubbish dump containing organic matter
• Ground where liquid wastes are spilled.

Que. 196. Which are the diseases transmitted by houseflies?

Ans. 196. The diseases transmitted by houseflies are –

• Typhoid & Paratyphoid fever
• Diarrhoea & dysenteries
• Cholera & gastroenteritis
• Amoebiasis
• Helminthic infestations
• Conjunctivitis & Trachoma
• Anthrax & Yaws.

Que. 197. How does fly transmit the diseases?

Ans. 197. Fly transmits the diseases by –

• Mechanical transmission
• Vomit drop
• Defecation

Que. 198. Enumerate fly control measures.

Ans. 198. The fly control measures are as follows –

• Environmental control
• Use of insecticides
• Fly papers
• Protection against flies e.g. screening
• Health education

Que. 199. Name the diseases transmitted by sand-flies.

Ans. 199. Kala-azar, sand-fly fever & oriental sore.

Que. 200. Name the disease in which tsetse-fly is a vector.

Ans. 200. Trypanosomiasis (sleeping Sickness).

Que. 201. Name the disease in which black-fly is a vector.

Ans. 201. Onchocerciasis.

Que. 202. Name the diseases transmitted by louse.

Ans. 202. Epidemic typhus, Trench fever, Relapsing fever & pediculosis.

Que. 203. Name the disease transmitted by rat-flea.

Ans. 203. Bubonic plague, Endemic typhus, chiggerosis & Hymenolepsis diminuta.

Que. 204. Name the disease transmitted by reduviid bug.

Ans. 204. Chagas disease.

Que. 205. How are rat-fleas passively transmitted?

Ans. 205. By –

• Their hosts
• Transport vehicles
• Humans & their luggage
• Movement of goods.

Que. 206. Which are the indices used in flea surveys?

Ans. 206. The indices used in flea surveys are as follows –

• General flea index
• Specific flea index
• Percentage incidence of flea species
• Rodent infestation

Que. 207. Which are the modes of transmission of diseases caused by rat flea?

Ans. 207. The modes of transmission are –

• Biting
• Mechanical transmission
• Faeces

Que. 208. Which are the measures involved in rat flea control?

Ans. 208. Insecticides, Repellents & Rodent control.

Que. 209. Name the diseases transmitted by hard ticks.

Ans. 209. Diseases transmitted by hard ticks are as follows –

• Tick typhus (Rocky Mountain spotted fever)
• Viral encephalitis
• Viral fevers
• Viral haemorrhagic fevers (KFD)
• Tularaemia
• Tick paralysis
• Human babesiosis

Que. 210. Name the diseases transmitted by soft ticks.

Ans. 210. Q fever, Relapsing fever & KFD.

Que. 211. Name the diseases transmitted by Trombiculid mite.

Ans. 211. Scrub typhus & Rickettsial pox.

Que. 212. Name the diseases transmitted by itch mite.

Ans. 212. Scabies.

Que. 213. Which are the measures involved in control of ticks & mites?

Ans. 213. Measures involved are as follows –

• Insecticidal control – Use of DDT, Chlordane, Lindane, malathion etc.
• Environmental Control
• Protection of Workers – Protective clothing impregnated with insect repellent.

Que. 214. Which are the measures involved in treatment of scabies?

Ans. 214.  Measures involved are –

• Benzyl benzoate
• HCH
• Tetmosol
• Sulphur ointment.

Que. 215. What is the mode of spread of scabies?

Ans. 215. By close contact or contaminated clothes.

Que. 216. Name organochlorine insecticides.

Ans. 216. DDT, HCH, dieldrin, chlordane, methoxychlor etc.

Que. 217. Name organophosphorus insecticides.

Ans. 217. Malathion, Fenthion, Abate, Chlorpyrifos etc.

Que. 218. Name insecticides of group Carbamates.

Ans. 218. Propoxur & Carbaryl.

Que. 219. How will you classify insecticides?

Ans. 219. Insecticides can be classified as follows –

• Contact poisons – Pyrethrum, DDT, HCH & Dieldrin.
• Stomach poisons – Paris green & sodium fluoride.
• Fumigants – e.g. Sulphur dioxide.

Que. 220. Name multiple dose poisons used against rats.

Ans. 220. Warfarin, diphacinone, coumafuryl & pindone.

Que. 221. What is the mode of transmission of diseases transmitted by rats/rodents?

Ans. 221. The mode of transmission is –

• Through bite (rat bite fever)
• Through contamination of food and water (Salmonellosis, Leptospirosis)
• Through rat flea (Plague, Typhus etc.)

Que. 222. What is the purpose of environmental health?

Ans. 222. The purpose is to create and maintain ecological conditions that will promote health and thus prevent disease.

Que. 223. What is the estimated basic physiological requirements for drinking water?

Ans. 223. About 2 litres per head per day.

Que. 224. Which water is the purest water in nature?

Ans. 224. Rain water.

Que. 225. What is the chief drawback of river water?

Ans. 225. It is always grossly polluted and is quite unfit for drinking without treatment.

Que. 226. Which process does make sea water usable for drinking?

Ans. 226. Desalting and demineralization process.

Que. 227. Why ground water is superior to surface water?

Ans. 227. Because the ground itself provides an effective filtering medium.

Que. 228. When deep well can become a health hazard?

Ans. 228. If it is open, poorly constructed & not protected against contamination.

Que. 229. Which kind of deep well did favour spread of Guinea worm disease in the past?

Ans. 229. Step wells.

Que. 230. What should be the location of well from the likely source of contamination if bacterial contamination is to be avoided?

Ans. 230. 15 m (50 feet).

Que. 231. What should be the location of the well in terms of its access to the community?

Ans. 231. The well should be so located that no user will have to carry water for more than 100 meters.

Que. 232. What is the beneficial health effects of hardness of water?

Ans. 232. As the hardness of water increases chance of death due to coronary heart disease decreases.

Que. 233. What is the use of WATER ACT?

Ans. 233. To provide legal deterrent against the spread of water pollution.

Que. 234. Which type of water filters are generally accepted as the standard method of water purification?

Ans. 234. Slow sand filters.

Que. 235. Which is the heart of the slow sand filter?

Ans. 235. Vital layer is the heart of the slow sand filter.

Que. 236. When it is uneconomical to run the slow sand filter?

Ans. 236. When the loss of head exceeds 1.3 meters.

Que. 237. How much bacterial load is reduced by slow sand filter in ideal conditions?

Ans. 237. Reduce total bacterial counts by 99.9 to 99.99% & E.coli by 99 to 99.9%.

Que. 238. How much bacterial load is reduced by the rapid sand filters?

Ans. 238. 98-99% of bacterial load.

Que. 239. What is the surface area of each unit of rapid sand filter bed?

Ans. 239. About 900 square feet.

Que. 240. When is filteration stopped and & the rapid sand filters are subjected to backwashing?

Ans. 240. When the loss of head approaches 7-8 feet.

Que. 241. Which compound is responsible for the disinfecting action of the chlorine?

Ans. 241. Hypochlorous acid and to a small extent due to hypochlorite ions.

Que. 242. When does chlorine act best as a disinfectant?

Ans. 242. When the pH of water is around 7.

Que. 243. What do you mean by break point?

Ans. 243. The point at which the chlorine demand of the water is met, is called the breakpoint. If further chlorine is added beyond the break point, free chlorine begins to appear in water.

Que. 244. What is the contact period of free residual chlorine to kill the bacteria and viruses?

Ans. 244. At least one hour.

Que. 245. What is the correct dose of chlorine to be applied for disinfection of water?

Ans. 245. The sum of the chlorine demand of the specific water plus the free residual chlorine of 0.5 mg/L constitutes the correct dose to be applied.

Que. 246. Which compound has replaced all the other chlorine derivatives in the disinfection of urban water supplies?

Ans. 246. Chlorine gas.

Que. 247. How much water is disinfected by a single chlorine tablet of 0.5 mg?

Ans. 247. Around 40 litres of water.

Que. 248. Why potassium permanganate should not be used for disinfecting wells?

Ans. 248. As it is not a satisfactory disinfecting agent.

Que. 249. How much good bleaching powder is required to disinfect the 1000 litres of well water?

Ans. 249. 2.5 gm of bleaching powder.

Que. 250. What is the standard prescribed for chlorides in drinking water?

Ans. 250. 200 mg/L. The maximum permissible level is 600 mg/L.

Que. 251. What does presence of ammonia in water indicate?

Ans. 251. Indicates possible bacterial, sewage & animal waste pollution.

Que. 252. How will you define hardness of water?

Ans. 252. Hardness of water may be defined as the soap destroying power of water. One meq/L of hardness producing ion is equal to 50 mg CaCO3 (50 ppm) in one litre of water.

Que. 253. What is the criticism of effective temperature scale?

Ans. 253. It ignores the effect of radiation from the surrounding structures.

Que. 254. What is the McArdle predicted 4 hour sweat rate as upper limit of comfort zone?

Ans. 254. A value of 3.

Que. 255. What is the main component of acidic rain that causes deforestation?

Ans. 255. Sulphuric acid (formed by combination of SO2 with water).

Que. 256. What are the adverse effects of inhalation of polycyclic aromatic hydrocarbons (PAH)?

Ans. 256. Cancers, gene mutations and toxic effects on reproduction.

Que. 257. What are the effects of improving indoor air quality?

Ans. 257. Improvement in indoor air quality might avert ARI & chronic respiratory diseases by 15% & of the respiratory tract cancers by 10%.

Que. 258. What should be the daylight factor in living room and kitchen?

Ans. 258. 8% in living room & 10% in Kitchen.

Que. 259. What is the unit of measurement of loudness of voice?

Ans. 259. Decibels (dB).

Que. 260. How will you measure frequency of noise?

Ans. 260. Hertz (Hz).

Que. 261. What are the range of frequencies audible to normal human ears?

Ans. 261. 20 – 20,000 Hz.

Que. 262. What does the zero line at the top of audiogram represent?

Ans. 262. Normal hearing.

Que. 263. When is auditory fatigue seen?

Ans. 263. When loudness is in the 90 dB region and at frequency of 4000 Hz.

Que. 264. What is the effect of exposure to noise above 160 dB?

Ans. 264. May rupture the tympanic membrane & cause permanent loss of hearing.

Que. 265. What is the use of the Key Pattern Station Barometer?

Ans. 265. For measuring the atmospheric pressure.

Que. 266. What is the use of kata thermometer?

Ans. 266. For measuring cooling power of air.

Que. 267. Which readings of dry kata and wet kata thermometer were regarded as indices of thermal comfort?

Ans. 267. A dry kata reading of 6 & above and a wet kata reading of 20 & above were considered as indices of thermal comfort.

Que. 268. Whether a P4SR of 2.5 litres in 4 hours is considered optimal for a working man?

Ans. 288. Yes, it’s true.

Que. 269. Which is the most satisfactory method of refuse disposal where suitable land is available?

Ans. 269. Controlled tipping or sanitary landfill.

Que. 270. Which is the method of choice of refuse disposal where suitable land is not available?

Ans. 270. Incineration.

Que. 271. Which is the method used for combined disposal of night soil or sludge and refuse?

Ans. 271. Composting.

Que. 272. Name a standard test which is an indicator of the organic content of the sewage.

Ans. 272. Biochemical oxygen demand (BOD).

Que. 273. Which is an established method of purifying sewage for small communities?

Ans. 273. Oxidation ponds.

Que. 274. What do you mean by term infestation?

Ans. 274. The lodgement, development & reproduction of the arthropods on the surface of body or in the clothing is called infestation.

Que. 275. What are the characteristics of eggs of anopheles mosquito?

Ans. 275. Eggs of anopheles mosquitoes are boat shaped and provided with lateral floats.

Que. 276. Name the insecticides which are the most effective Larvicides?

Ans. 276. Synthetic insecticides e.g. Fenthion, Chlorpyrifos and abate.

Que. 277. Whether sand flies are generally confined to within 50 yards of the breeding places?

Ans. 277. Yes, it’s true.

Que. 278. For which diseases, Cyclops act as the intermediate host?

Ans. 278. Guinea worm & fish tapeworm diseases.

Que. 279. Name the chemical extensively used for the fumigation of rat burrows.

Ans. 279. Cyanogas.

Que. 280. Which is the least toxic organophosphorus compound?

Ans. 280. Malathion.

Que. 281. Whether trans-ovarian transmission through successive generations are seen in ticks?

Ans. 281. Yes, it’s true.

Que. 282. Which are the most commonly affected parts of the body in Scabies?

Ans. 282. Hands & wrists.

Que. 283. How will you confirm the diagnosis of scabies?

Ans. 283. Confirmation of diagnosis of scabies can be done by searching for the parasite in the skin debris under the microscope.

Suggested Further Readings –

• Park; Park’s textbook of Preventive & Social Medicine, 26^th edition, 2021
• Bhalwar; textbook of Public health & Community Medicine, AFMC-WHO, 1^st edition, 2009
• Mahajan & Gupta; Textbook of Preventive & Social Medicine; 4^th edition
• AH Suryakantha; Community Medicine with Recent Advances, 3^rd